The chords are below. If you listen to it while looking at the chords you'll figure out the rhythm. I'm adding in some 7ths and 9ths, so feel free to mess around with it, but the chords below will get you through the whole thing. Enjoy!
rah-rah intro: Am - G (x2)
just dance verse: Am - C - G - Dm (x4)
just dance pre-chorus: F - Am (x2)
bad romance pre-chorus: F - G - E7 - Am - G (x2) F - G
just dance chorus: Am - C - G - Dm (x4)
love game part: Am - G (x2)
poker face/paparazzi verse: Am - F - G (x2) Dm - G Am - F - G (x2) Dm - G